1. Field of the Invention
The present invention relates, in general, to a DNA segment. In particular, the present invention relates to a DNA segment coding for a polypeptide having an amino acid sequence corresponding to RhoNUC, a polypeptide having an amino acid sequence corresponding to RhoNUC, antibodies to RhoNUC, a recombinant DNA molecule, cells containing RhoNUC, and methods of producing and using the polypspride and DNA segment.
2. Background Information
Repair processes in the yeast Saccharomyces cerevisiae are under extensive genetic control involving over 50 genes; among these are genes that function in recombinational repair as well as normal meiotic and mitotic recombination (Kunz, B.A., and R. H. Haynes (1981) Annu. Rev. Genet. 15:57-89; Game, J.C. (1983) in: Yeast Genetics, Fundamental and Applied Aspects (eds. Spencer, J.F.T., Spencer, D., and Smith, A.) pgs. 109-137, Springer-Verlag New York, Inc., New York, and Resnick, M.A. (1987) in: Meiosis (ed. Moens, P.), pgs. 157-212, Academic Press, New York). Deoxyribonucleases are expected to play a role in many repair processes since they enable the excision of damaged DNA and provide a means for heteroduplex formation and processing in recombination. Several deoxyribonucleases have been shown both genetically and biochemically to function in recombination and repair. For example, the nuclease activity associated with the Escherichia coli recBCD proteins is required for much of host recombination and also for chistimulated lambda bacteriophage (Chaudhury, A.M., and G. R. Smith (1984) Proc. Natl. Acad. Sci. (USA) 81:7850-7854). Holloman and Holliday (J. Biol. Chem. 248:8107-8113, 1973) have described nuclease .alpha. from the eucaryote Ustilago maydis that is required for recombination and DNA repair. Because of the complex genetic control involving two genes, the specific role of this nuclease has not been ascertained. An endo-exonuclease from Neurospora crassa has also been implicated in recombination and repair (Chow, T.Y.-K, and M. F. Fraser (1979) Can. J. Biochem. 57:889-901; Chow, T.Y.-K, and M. F. Fraser (1983) J. Biol. Chem. 258:12010-12018, and Ramotar, D., et al. (1987) J. Biol. Chem. 262:425-431). The phenotypes of mutants deficient or altered in nuclease activity include meiotic sterility and sensitivity to ultraviolet light, X-rays, and/or alkylating agents (Fraser, M.J., et al. (1990) in: DNA repair and mutagenesis in Eucaryotes (Generoso et al., eds) pgs. 63-74, Plenum Publishing Corp., New York). A similar endo-exonuclease has also been isolated from Aspergillus nidulans (Koa, H., et al. (1990) Biochem, Cell. Biol. 68:387-392) and from mammalian mitochondria (Tomkinson, et al., (1986) Nucl. Acids Res. 14:9579-9593).
An endo-exonuclease, RhoNUC, from S. cerevisiae was isolated and characterized and was suggested to function in both repair and recombination (Chow, T.Y.-K, M. A. Resnick (1987) J. Biol. Chem. 262:17659-17667, and Chow, T.Y.-K, and M. A. Resnick (1988) Molec. Gen. Genet. 211:41-48; Because of the chimeric nature of the endoexonucleasei this protein is now referred to as RhoNUC, rather than the original yNUCR reported in these papers and the gene encoding RhoNUC is named RNC1 for Rho-associated-Nuclease). Several properties of RhoNUC resemble those of the E. coli recBCD nuclease. The RhoNUC activity in both mitotic and meiotic cells is greatly influenced by a functional RAD52 gene. The RAD52 gene product is required for mitotic and meiotic recombination and for the repair of double stranded breaks in DNA. Mutants deficient in the gene product (rad52) cannot proceed properly through meiosis. Meiotic recombination is abolished in rad52 mutants, and cells die as they enter the meiotic cycle. In rad52 mutants, the mitotic level of the endo-exonuclease is less than 10% of the wild type level, and no increase is observed during meiosis (Resnick, M.A. et al. (1984) Molec. Cell. Biol. 4:2811-2817).